The present invention relates to a catheter for delivery of implant devices of the general type comprising a loading means for enveloping the implant within a catheter tube and a releasable implant gripping means.
There are many forms of medical implant devices, deployed transvascularly by means of a catheter, which are used where there is a requirement to occlude a vessel, fill a void or plug a defect in the treatment of medical conditions, whether they be acute or chronic situations or cosmetic situations.
These medical implant devices are delivered either transarterially or transvenously. The medical implant device is loaded in a folded or collapsed position within a tip of a catheter. The tip of the catheter is directed to the defect which is to be repaired and then the medical implant device is delivered from the catheter. Once out of the catheter the medical implant device is expanded to its full size to occlude the defect. Many of the known medical implant devices used are unsuitable for some applications because of their size and rigidity and we have proposed in certain co-pending patent applications the provision of a replacement technology for conventionally used coils, wire frame occlusion devices and the like. These improved implant devices have included the provision of highly compressible implant devices such as those having a compressible porous polymeric structure. One of the problems, however, with compressible devices and indeed many other devices is that they often do not react favourably to the conventional way of loading them in the catheter, which comprises pushing or pulling the implant into an end of the catheter. Very often by their very nature which allows them expand and assume the correct shape within the void this is the very construction that makes them difficult to push and manipulate. This also applies to other types of devices as well as implants having a compressible porous polymeric structure. Indeed what is required with most of these implants which can be loosely described as being expandable is that they be correctly compressed within the catheter. It is also desirable that if the implant device is initially deployed incorrectly or in the wrong location that the implant device can be easily loaded again in a collapsed position within the catheter for redeployment.
U.S. Pat. No. 5,683,451 discloses apparatus and a method for endoluminal placement of intraluminal tubular prostheses such as grafts and stents. The devices are collapsed within a distal end of a delivery catheter by a set of spaced-apart hard elongate runners mounted at a distal end of an inner catheter slidable within the delivery catheter.
WO 98/14224 discloses apparatus and a method for retrieving partially deployed balloon expandable stents from within a vein or artery. The apparatus has a grasping device comprising either an expandable tube or a plurality of spaced-apart nitinol fingers with elastomeric web stretched therebetween. The tube or fingers can be manipulated to open to grasp a stent and then closed to grip the stent for withdrawal into a catheter.
U.S. Pat. No. 5,026,277 discloses a device for the deployment or retraction of a self-expanding stent in a body canal. The device has a tubular outer sleeve and an inner core slidable within the sleeve, the stent being collapsed against the core and being held in the collapsed state between the core and the outer sleeve for deployment.
It is an object of the present invention to provide a catheter that has the ability to deliver devices that don""t have axial stiffness.
According to the invention there is provided a catheter for transvascular deployment of a radially compressible medical device, comprising an elongate tubular outer body having a proximal end and a distal end, a tubular housing being formed at the distal end of the body for reception of the medical device in a collapsed state, a deployment means for engagement with the medical device being movable through the housing to move the medical device between a collapsed stored position within the housing and a deployment position externally of the housing, and loading means for radially collapsing the medical device for engagement within the housing, the loading means being movable relative to the body for engagement with the medical device,
characterised in that the loading means comprises a tubular sheath having a proximal end and a distal end, the distal end of the sheath being slidably mounted within the distal end of the body,
the distal end of the sheath having a tubular side wall with two or more slits in the side wall of the sheath extending proximally from a distal end of the sheath,
the slits sub-dividing the tubular side wall of the distal end of the sheath into a number of complementary tube sections which are movable between a closed position defining a tubular housing for reception of the medical device and an open position to enlarge the distal end of the sheath when the distal end of the sheath is moved outwardly of the distal end of the body.
By using a tubular loading means which is movable relative to the medical device for its securement, it is possible to grip the medical device in whatever way one requires and thus ensure that, for example, with a compressible or distortable medical device it is not compressed in an undesired way. Further, as the loading device is tubular, it provides continuous support fully around the medical device ensuring an even compression of the medical device. This is particularly desirable with foam type medical devices which do not have a support frame and so are easily distorted. The tubular loading means allows controlled compression of such medical devices so that they will open in a desired manner upon deployment.
In a preferred embodiment the slits in the distal end of the sheath comprises two or more circumferentially spaced-apart axially extending slits in the distal end of the sheath.
In another embodiment the slits in the distal end of the sheath comprise two or more circumferentially spaced-apart helical slits in the distal end of the sheath.
In a further embodiment each tube section has an inner end hingedly connected to the sheath body by a hinge. Preferably each hinge is integrally formed with the sheath.
Conveniently each hinge may be biased to urge the tube section towards the open position.
In another embodiment a pair of slits are provided in the distal end of the sheath, sub-dividing the distal end of the sheath into two complementary tube sections hingedly connected at their inner ends to the sheath.
In a further embodiment three slits are provided in the distal end of the sheath, sub-dividing the distal end of the sheath into three complementary tube sections hingedly connected at their inner ends to the sheath.
In a further embodiment four slits are provided in the distal end of the sheath, sub-dividing the distal end of the sheath into four complementary tube sections hingedly connected at their inner ends to the sheath.
In another embodiment the deployment means for the medical device is a guidewire extending through the sheath.
Conveniently the catheter body is formed from a low friction material.